The present application concerns compositions comprising calcium cyanamide and methods for their use including, without limitation, in industry and farming, decomposition (composting), odor and organism inhibition, nutrient stabilization, fertilizing and soil amending.
Commercial calcium cyanamide (CaNCN) is actually a mixture of several components formed during or remaining after production of the desired calcium cyanamide compound. Additional components found in commercial calcium cyanamide include calcium oxide (CaO), calcium carbide (CaC2), graphite carbon (C) and oxides of iron, aluminum, and silicon.
Typically for one reason or another, commercial calcium cyanamide is treated to alter the form of cyanamide or remove components remaining after manufacture. For example, because calcium cyanamide is a slow acting fertilizer that is sparingly soluble in water, it is often factory converted to water-soluble molecular cyanamide (H2NCN) which is faster acting and a higher analysis source of nitrogen. In this process, calcium cyanamide is forced to dissolve in water by precipitation of calcium ions (Ca2+) as calcium carbonate (CaCO3) and by acidification to convert initially formed cyanamide ions (NCN2xe2x88x92) into acid cyanamide ion (HNCNxe2x88x92) and then into molecular cyanamide, which predominates at a pH of 4.5-5.5. Insoluble calcium carbonate and graphite carbon which may be entrained in the calcium carbonate are then removed by filtration.
Calcium oxide and calcium carbide are also removed during this process. In the case of calcium carbide, the carbide ion reacts with water to form acetylene that is lost as a gas to the atmosphere. Thus, it is seen that many of the components originally in commercial calcium cyanamide are converted, removed, or lost.
A. Calcium
Calcium ions (Ca2+) are present in most organic matter and are necessary for many enzymatic reactions, including those that facilitate energy use by living organisms. Furthermore, calcium ions aid in soil reclamation by acting to flocculate soil and permit water percolation. Additionally, calcium tends to enhance the breakdown of organic matter through these and other actions.
While calcium ions are abundant in nature in the form of limestone (calcium carbonate, CaCO3), they are not readily available for uptake because of the relative insolubility of calcium carbonate. From this is seen the need to stabilize calcium ions in soluble form to enhance the speed of calcium uptake into organic matter, both living and dead, to aid plant growth and soil reclamation.
Completely ignored to this date is calcium cyanamide""s potential as a source of stabilized Ca2+ that can rapidly enter plants and flocculate soil. While promotional literature does mention calcium cyanamide as a possible soil amendment, unstabilized it is no more useful than inexpensive mined lime (CaCO3). However, if the soluble forms of calcium could be stabilized, it would provide added value to calcium cyanamide.
Stabilizing soluble calcium ions at the immediate first hydrolysis step during the production of molecular cyanamide from commercial calcium cyanamide has been overlooked. Typical descriptions of the hydrolysis of calcium cyanamide indicate conversion directly to molecular cyanamide and calcium carbonate. Furthermore, some prior art hydrolysis schemes ensure complete loss of soluble calcium through CO2 enrichment during aerobic hydrolysis, to provide calcium free, acid stabilized molecular cyanamide or soluble acid cyanamide salts. Such processes leave lime (CaCO3) blackened by graphite carbon (C) in huge, now environmentally suspect piles, behind calcium cyanamide factories. Given the huge energy costs of initial calcium cyanamide production and subsequent analog production costs, it is unfortunate that a valuable nutrient such as calcium is left behind in piles of black lime for the sake of obtaining only nitrogen fertilizer from calcium cyanamide. The wastefulness of this practice is highlighted in that the major portion of commercial CaNCN is calcium. It is therefore desirable to stabilize and deliver the calcium component of calcium cyanamide for decomposition (composting) enhancement, odor and organism inhibition, plant nutrition, and soil flocculation.
B. Nitrogen
Nitrogen, in its molecular form (N2) comprises approximately 78% of the earth""s atmosphere. Nitrogen is a component of all proteinaceous matter found in living organisms, but only a few organisms (such as nitrogen-fixing bacteria) are able to directly capture atmospheric nitrogen and add it to the biosphere.
Proteinaceous matter, contained in dead and decaying organic matter and additionally in the excreta of animals represents a vast potential source of nitrogen for growth of living organisms. However, in proteinaceous form, nitrogen is insoluble and unavailable to living organisms except through the action of decomposers, which release nitrogen in the forms NH3, NH4+, NO2xe2x88x92, and NO3xe2x88x92. These forms can be utilized by plants and allow nitrogen to reenter the living biosphere.
In many instances the rate at which nitrogen becomes available from decomposing (composting) organic matter is insufficient to provide rates of plant growth that are desired by modem agriculture. Thus, there arises a need to supplement available nitrogen in soil and/or increase the rate at which nitrogen becomes available to plants from decomposing organic matter.
Modern agriculture has chosen to pursue a strategy of supplementing plant available nitrogen through the use of high analysis nitrogen fertilizers, such as inexpensive urea, ammonia, ammonium compounds, and nitrates. Concurrently, use of calcium cyanamide, the first commercially available high analysis fertilizer, has declined due to the high cost of its manufacture and to the handling, shipping, and phytotoxicity problems it poses.
While high analysis nitrogen fertilizers can provide abundant nitrogen for rapidly growing plants, their use has produced some undesirable consequences, such as leaching of nitrates into groundwater and losses of volatile ammonia to the atmosphere. These are also problems associated with composting and applying animal excreta directly to soils. Thus, it is desirable to provide compositions and methods that promote release of nitrogen from proteinaceous materials, yet slow its loss to the atmosphere and from soil. It is also desirable to provide compositions and methods that stabilize and extend the residence time of high nitrogen analysis fertilizers in the plant root zone.
C. Calcium and Nitrogen
Plants deficient in calcium but provided with an abundance of nitrogen are prone to parasitic organisms. Conversely, plants with high ratios of calcium to nitrogen resist parasitic organisms. It is also known that it is difficult to provide plants with calcium in direct proportion to the rate at which they can absorb soluble nitrogen forms, even if calcium and nitrogen are provided as water-soluble calcium nitrate (CaNO3). Slow acting calcium sprays and expensive chelated forms of calcium have been reported not to cure calcium deficiencies observed during intensive nitrogen demanding vegetable production in California (Crop Notes, UC Extension, Salinas, Calif., Jul. 2000). Therefore, it would be desirable to have compositions and methods that stabilize soluble calcium and promote calcium uptake by plants in proportion to nitrogen uptake, thereby conferring parasite resistance to the plants.
D. Calcium Cyanamide (CaNCN)
Calcium cyanamide which comprises 44% calcium and 24% nitrogen was first made in the late 1800s, as part of a search for a high analysis nitrogen source for industry and agriculture to replace low analysis (1- less than 12%) excreta deposits. It is produced in 1000 to  greater than 3,000xc2x0 C. electric arc furnaces by burning black coal and white limestone in the presence of atmospheric nitrogen. Energy costs represent the bulk of the cost of production of calcium cyanamide.
Because calcium cyanamide is slow acting, one application at a rate of 1000 to 2000 lbs/acre lasts all growing season long. However, when calcium cyanamide is applied at these typical season long rates, particularly in cool and or dry conditions, it is necessary to delay planting until the high concentrations of plant penetrating initial hydrolysis products of calcium cyanamide, which are toxic to seeds and seedlings (phytotoxic), dissipate. Furthermore, because calcium cyanamide in its noxiously dusty irregular granule form is difficult to calibrate, its application may be haphazard so that one part of a field may be ready for planting while others exhibit persistent phytotoxicity. The phytotoxic characteristics of calcium cyanamide also make even repeated dry applications at lower rates impractical.
The observation that calcium cyanamide exhibits phytotoxicity led to its use as a herbicide. However, its use as a herbicide has largely been dropped in favor of modem herbicides.
For the reasons above, use of dry calcium cyanamide has decreased and presently, it is no longer used in the United States. Worldwide, its use is largely restricted to rice cultivation, where hot, wet conditions quickly degrade and remove other nitrogen fertilizers, such as urea, from the soil.
Calcium cyanamide is more typically converted to faster acting and higher analysis forms of nitrogen. For example, calcium cyanamide may be aerobically hydrolyzed in the presence of carbon dioxide to provide calcium free urea (42% N). Other high analysis nitrogen forms which are produced from calcium cyanamide include calcium free, dicyandiamide ((HNCN)2, 66% N) and molecular cyanamide (H2 NCN, 66% N). These forms have found use in both agriculture and the production of many of today""s industrial polymer chemicals and medicines. However, plant beneficial calcium is not a part of these products.
It would be a benefit to provide compositions and methods that exploit the slow acting nature of calcium cyanamide yet provide immediately available plant nitrogen without phytotoxic consequences. It would also be a benefit if such compositions and methods made it easier to calibrate applications of calcium cyanamide and facilitated repeated smaller applications throughout the growing season. Furthermore it would be an advantage if these benefits were achieved at more economical rates of application and enabled more of the components that exist in commercial calcium cyanamide to be utilized.
These benefits have been partially realized by Hartmann, as described in U.S. Pat. Nos. 5,698,004 and 5,976,212, which are incorporated herein by reference. Contrary to teachings against fertilizing plants with the initial hydrolysis products of calcium cyanamide (because of their phytotoxicity), Hartmann has worked to provide easily deliverable stable hydrolyzed ionic CaNCN solutions, containing plant penetrating acid cyanamide anions directly to plants. Caustic is added to such ionic solutions to maintain a pH that favors the acid cyanamide ion. The calcium cyanamide solutions taught in these prior patents are sprayable if insolubles, such as calcium carbonate and residual carbon, are retained by a means of filtration. Balls and clumps of calcium carbonate that entrain otherwise sprayable carbon tend to plug pumping and spraying equipment. Because carbon is also beneficial to plants and soils it would be advantageous if there existed methods of preventing formation of such balls and clumps, so that more calcium remained soluble, filtration was unnecessary, and the residual insoluble carbon found in commercial calcium cyanamide could be maintained in a sprayable slurry. Furthermore, it would be a benefit if it were possible to maintain a pH favorable to acid cyanamide ions without having to add caustic to overcome the tendency of these solutions to drop in pH.
E. Urea
Urea, today, is made in approximately 75 factories worldwide with a total capacity approaching 100,000,000 tons annually. Dry, water-soluble urea is a low cost, fast acting, and easily calibrated soluble nitrogen form. However, urea is recognized to undergo rapid hydrolysis, which may lead to ammonia gas release and/or losses due to nitrate leaching. Urea and excreta hydrolysis also contribute large amounts of the greenhouse gas CO2. In fact, urea and decomposed proteinaceous animal excreta containing urea are now considered so environmentally threatening that farmers using such fertilizers have already been subject to fines and judgments ($30,000 to $300,000) for violation of clean water laws that regulate nitrates. It would therefore be desirable to provide compositions and methods that allow urea and animal excreta to be utilized as fertilizers without ammonia loss or rapid leaching of nitrates.
There are two basic prior art approaches to simultaneously making urea-derived nitrogen available to plants for longer periods and reducing nitrate contamination. The first is to slow urea dissolution. The second is to slow the conversion of urea to nitrate by soil microorganisms, either by inhibiting the action of urease or inhibiting nitrification, or both.
Urea dissolution control may be accomplished by coating urea with hydrophobic substances, such as sulfur, to produce slow release granules. U.S. Pat. No. 4,081,264 to Ali exemplifies this technology. Ali describes encapsulated slow release fertilizers prepared by coating a fertilizer substrate (e.g. urea) with molten sulfur. Sulfur coated urea particles are brittle so they are often coated with a plasticizing substance, such as bitumen, to increase their mechanical strength. Finally, another coating of an inorganic material, such as talc, may be required to provide a free flowing material. While slow release granules can extend nitrogen availability throughout the growing season and reduce nitrate leaching, they are too costly for general agricultural use, especially in light of their lower nitrogen content.
Urease inhibitors serve to slow the conversion of urea to ammonium ions. Such inhibitors include phosphoric triamides, such as N-(n-butyl)thiophosphoric triamide (NBPT) (see for example U.S. Pat. No. 4,530,714). Phosphoric triamides however are difficult to handle and susceptible to decomposition. Efficient incorporation of phosphoric triamides into granular urea-containing fertilizers may be accomplished through the use of liquid amide solvents, but use of such solvents in the granulation process increases the cost of such fertilizers.
Nitrification inhibitors, when combined with urea, ammonia, and ammonium salt fertilizers, can also serve to reduce nitrate leaching. Known nitrification inhibitors include dicyandiamide (DD) and N-Halamine compounds. Dicyandiamide, which is made from calcium cyanamide, also functions as a nitrification inhibitor. It is however, short-lived in hot soils.
While calcium cyanamide is believed to function as both a urease and nitrification inhibitor, direct addition of calcium cyanamide to urea is warned against because the residual calcium oxide in commercial calcium cyanamide promotes ammonia volatilization, especially under wet conditions (Nianzu et al., Fertilizer Research, 41: 19-26, 1995).
What is need therefore are compositions and methods that make it possible to take advantage of calcium cyanamide""s potential to mitigate nitrate leaching following application of urea. Furthermore it would be advantageous to provide compositions and methods that make it possible to combine commercial calcium cyanamide directly with urea, even in wet conditions, and preserve the calcium oxide component of the calcium cyanamide and/or its water dissolution products.
F. Cyanamide Dissolution and Hydrolysis Products
When calcium cyanamide first dissolves in water it produces calcium ions (Ca2+) and cyanamide ions (NCN2xe2x88x92) as products. The cyanamide ion is very basic and reacts with water to form the acid cyanamide ion (HNCNxe2x88x92). The acid cyanamide ion is amphoteric, i.e. it can act as either an acid or a base. If the acid cyanamide ion acts as an acid it will revert to the cyanamide ion and if it acts as a base it will react to form molecular cyanamide (H2NCN). The form that cyanamide takes in solution will depend upon the pH of the solution, but molecular cyanamide is favored at pH""s below 10.3, which are typical of soils. Molecular cyanamide may then undergo hydrolysis to form urea, which may further react to form ammonium ions, which may further be converted to volatile ammonia or to nitrate.
As stated previously, the acid cyanamide ion is plant and organism penetrating. Once absorbed by plants, the acid cyanamide ion lasts only 2-4 hours before it forms urea, which lasts 4-8 hours. Both acid cyanamide and urea stimulate arginine production in plants, however, cyanamide stimulates arginine production 20 times more effectively than urea. Arginine production is related to activation of both plant reproductive responses and disease and pest resistance in plants. Such activation is termed xe2x80x9cSystemically Activated Resistancexe2x80x9d or SAR (see for example, Kunz et. al., Zeitschrift fur Plantzen Krankheiten und Flanzenschutz, 61: 481-521, 1954; Lovatt et. al., Proceedings California Plant and Soil Conference 1992 and 1995; Wunsch et. al., Zeitshrift fur Pflanzenphysiology, 72: 359-366, 1974; and Von Fishbeck et. al., Zeitschrift fur Planzen Krankheiten, 71: 24-34, 1964). Therefore, compositions and methods that stabilize and provide acid cyanamide ions to plants over long periods of time are desirable for producing fruitful, parasite free plants.
When CaNCN is applied at fertilizer rates, atop warm, wet soil, rapid uncontrollable aerobic hydrolysis occurs, moving initially soluble calcium to insoluble calcium forms and cyanamide ions to urea, then gaseous ammonia at that location. A need is thus seen to economically stabilize initial pre-hydrolysis soluble acid cyanamide ions and calcium ions in high dilutions so that they can rapidly percolate to target sites of choice where the ions can be absorbed by plants and aid in maintaining soil porosity.
In addition, USDA geneticists have recently succeeded in placing the Cah gene from natural soil cyanobacteria into crop plants cells to make them resistant to the phytotoxicity of acid cyanamide(HNCN) ions. This gene permits a plant to rapidly convert acid cyanamide ions to non-phytotoxic urea. The use of CaNCN fertilizer as a dual use foliar herbicide and nitrogen source is envisioned as an attractive alternative to single use herbicides (USDA Agricultural Research/July 1998). Thus, should crop plants with the Cah gene obtain regulatory approval, a need for target site delivery of a stabilized source of acid cyanamide ions will arise.
G. Calcium Carbide
Calcium carbide (CaC2), the initial product of arc furnace burning ( greater than 3,000 C.) of coal and lime remains a residual in commercial calcium cyanamide. Hydrolyzing calcium carbide produces water-soluble acetylene gas (C2H2), which is about 50% as soluble in water as CO2 but less dense. Due to Department of Transportation regulations, the calcium carbide content of calcium cyanamide must be reduced below 0.1% before it can be shipped. Regardless, enough residual carbide exists in commercial calcium cyanamide to produce a noticeable carbide gas odor upon opening a sealed vessel of water in which calcium cyanamide has been mixed.
Because the residual calcium carbide content of calcium cyanamide is typically factory reduced for shipping by sprinkling it with water in the presence of atmospheric carbon dioxide, the soluble calcium content of commercial calcium cyanamide is effectively reduced by production of calcium carbonate. Therefore, compositions and methods that eliminate the need to remove calcium carbide prior to shipment would be desirable. Furthermore, methods and compositions that take advantage of the residual calcium carbide component of calcium cyanamide are desirable.
H. Calcium Oxide
Calcium oxide, a by-product of calcium cyanamide production, is considered a nuisance for at least two reasons. First, calcium oxide readily absorbs carbon dioxide from the atmosphere to form calcium carbonate. Calcium carbonate, has a density that is lower than calcium oxide and therefore occupies more space than the calcium oxide from which it forms. When calcium oxide reacts to form calcium carbonate within particles of commercial calcium cyanamide, the result is an expansion that leads to cracking and noxious dusting of the calcium cyanamide product. Second, calcium oxide reacts with water to form calcium hydroxide, a strong base. During production of molecular cyanamide from calcium cyanamide, the calcium oxide component of the commercial calcium cyanamide product makes it necessary to add additional acid to lower the pH to 4.5-5.5, thus adding expense to the molecular cyanamide product.
As discussed previously, calcium oxide is also a potential source of calcium ions from commercial calcium cyanamide. Therefore, it is desirable to preserve the soluble calcium that is contained in the calcium oxide. Furthermore, as also discussed above, it is advantageous to prevent production of insoluble calcium carbonate from calcium oxide if spray application of calcium cyanamide is desired.
I. Organics
In recent years odorous xe2x80x9cgreenhouse gasxe2x80x9d emissions, coliform bacteria, leachable nitrogen, and phosphate from concentrated animal feeding operations has become an environmental concern, both in the US and the throughout the world. Such concerns have prompted US Federal, State, and world wide funding of inspections of livestock operations for compliance with herd size and odor, disease and water nutrient level mitigation measures. For example, in the Netherlands, animal operations must account for and balance every single unit of input with output units. Aerobic composting that wastefully releases nitrogen and carbon into the atmosphere and storage of animal wastes in vast aerobic, odorous lagoons still remain the principal available mitigation measures short of reducing herd size and suffering negative economic consequences.
Thus there appears a vast urgent need to provide an economical, practical and rapid, non-gas releasing, composting alternative to animal feeding sites. Such an alternative method of composting would desirably reduce the odor and disease causing organisms associated with animal wastes while resulting in a fertilizer composition that contains stabilized nutrients which promote sustained growth and parasite resistance in plants and serve as effective soil amendments.
J. Metals
Metals are an essential to life. However, metals are increasingly being leached below plant root zones due to the increased use of soluble, acid forming nitrogen plant foods. One solution to this problem is to apply lime to soils because many metals are less likely to leach from soils of higher pH. Lime, albeit inexpensive, requires tons per acre and considerable application expenses to achieve modest increases in soil pH. As explained earlier, lime is virtually insoluble, thus slow to release soluble calcium and pH increasing carbonate ions. Thus, lime only slowly raises soil pH, especially at depth in the soil where it is desired to immobilize metals near plant roots so that they are available to the plants. What are needed are compositions and methods that can supply metal micro-nutrients quickly to plant root zones and stabilize them in the root zone by raising the pH of the soil at depth. Because commercial calcium cyanamide contains approximately 2% oxides of the elements iron, silicon, and aluminum, it would also be advantageous to make use of calcium cyanamide as a source of these micro-nutrients while simultaneously providing for their stabilization in the soil.
Carbon dioxide and catalytic converter metal deposits from auto exhausts are apparently resulting in metal leaching into groundwater along roadsides. Acidic conditions develop along roadsides through carbon dioxide dissolution in rain water and decomposition of plant matter. These conditions foster leaching of deposited metals, some of which are toxic. For example, although lead is no longer a component of most gasoline products, lead contamination remains a problem where high concentrations of the metal were deposited in the past. Thus, there is a need to slow or prevent leaching of metals from soils along roadsides. Again, application of lime is one possible solution, but what are needed are compositions and methods that can provide metal stabilization in soils without the limitations of lime discussed previously.
The compositions and methods of the present invention satisfy the background needs and offer the desired advantages identified above. Generally, the disclosed compositions and methods provide for stabilization, controllable release, and enhanced efficiency of the components of commercial calcium cyanamide. When calcium cyanamide is combined according to the disclosure with nitrogen containing materials, co-activation and stabilization occurs, providing synergistic responses from the components of both the calcium cyanamide and of the nitrogen containing materials.
In one aspect, the compositions and methods of the disclosure may be understood in analogy to the art of canning or freeze-drying, in which food is peeled, cut and slightly cooked, imbibed with liquids, then mechanically sealed or freeze dried so that the initially exposed and softened elements are stabilized and preserved. In much the same way, the compositions and methods may be thought of as initially exposing and then preserving the beneficial initial dissolution and hydrolysis products of the components of commercial calcium cyanamide. Thus, an overall objective is to free, stabilize in soluble or suspendable form, activate, and preserve all the components initially available from commercial calcium cyanamide so that they may be controllably released together to provide full, new effects at a later time.
In some embodiments, the disclosure provides granular materials that meet the objectives of freeing, stabilizing, activating and preserving the components of commercial calcium cyanamide. Such granular materials generally comprise about 0.1 to about 40% of the total weight as calcium cyanamide and about 60 to about 99.9 percent of the total weight as urea. In particular embodiments, the material comprises calcium cyanamide homogeneously mixed with the urea. In other particular embodiments, the granular material is heterogeneous and comprises a core and a shell.
The core of the heterogenous granular material may comprise a substance selected from the group consisting of calcium cyanamide, urea, and mixtures thereof and the shell may comprises a substance selected from the group consisting of calcium cyanamide, urea, and mixtures thereof. In a more particular embodiment, the core comprises calcium cyanamide and the shell comprises urea.
In some embodiments, the granular materials further comprise at least one additional nitrogen containing material, for example natural organics, such as manure, ammonium salts, such as ammonium sulfate, ammonium chloride, ammonium monophosphate, ammonium diphosphate, ammonium citrate, ammonium nitrate, calcium ammonium phosphate, and mixtures thereof. In other embodiments, the granular materials further comprise at least one non-nitrogen plant nutrient, for example, a non-nitrogen plant nutrient selected from the group consisting of phosphorous, potassium, iron, copper, zinc, manganese, boron, magnesium, molybdenum, sulfur, and mixtures thereof. In yet other embodiments the granular material comprises at least one nitrogen containing compound and at least one non-nitrogen plant nutrient which may for example be selected from the nitrogen containing compounds and non-nitrogen plant nutrients that are specifically listed above. Such nitrogen containing compounds and non-nitrogen plant nutrients may be combined with urea, calcium cyanamide, or both.
In some embodiments, heterogeneous compositions comprising a calcium cyanamide core and a urea shell, that exhibit particularly effective dissolution, activation, and stabilization of calcium cyanamide components, are provided. In particular embodiments, the calcium cyanamide core is from about 0.1 to about 40 percent by weight and the urea shell is from about 60 to about 99.9 percent by weight. In a more particular embodiment, the calcium cyanamide core comprises from about 0.1 to about 10 percent of the total mass of the composition and the urea shell comprises from about 90 to about 99.9 percent of the total mass of the composition.
Heterogeneous core-shell materials typically exhibit an apparent react zone at the interface between the core and the shell that may be indicative of co-mingling of the initially reacted calcium cyanamide core and the urea shell during preparation of the material. It is postulated the react zone extends from inside the core out into the observable halo in the urea shell. The react zone may be responsible for the rapid and enhanced reactivity of these compositions.
Heterogenous materials comprising calcium cyanamide and urea may be granular and may further comprise at least one additional nitrogen containing compound and/or at least one non-nitrogen plant nutrient. In particular embodiments, the materials may further comprise a hardening agent, such as formaldehyde, in, for example, the urea shell.
The disclosure provides methods for making a heterogeneous granular composition by providing a calcium cyanamide particle and coating the calcium cyanamide particle with urea. In particular embodiments, the calcium cyanamide particle is from about 0.1 to 40 percent by weight of the final heterogeneous granular composition, for example, about 0.1 to about 10 percent by weight of the final heterogeneous granular composition. In other embodiments, the calcium cyanamide particle is coated with molten urea which, may be sprayed onto the calcium cyanamide particle to form the heterogeneous granular composition. In more particular embodiments, the molten urea further comprises from about 0.001% to about 20% water, that may serve to assist in initial activation of the components of the calcium cyanamide particle and stimulate formation of a react zone at the interface between the calcium cyanamide core and the urea shell.
In some embodiments, a calcium cyanamide particle is coated with successive layers to form a heterogeneous granular composition. In particular embodiments the successive layers are all urea layers. However in other particular embodiments, at least one of the successive layers comprise materials selected from the group consisting of urea, ammonium sulfate, ammonium citrate, ammonium phosphate, calcium ammonium nitrate, calcium nitrate, sodium nitrate, ammonium chloride, and mixtures thereof.
Methods for making homogeneous solid compositions comprising calcium cyanamide are also disclosed. In one embodiment, a homogeneous solid composition is made by combining calcium cyanamide, a nitrogen containing material, and water, where the amount of water is at least 14 times the weight of the dry calcium cyanamide, to form an aqueous material. Aeration of the aqueous material is inhibited and the aqueous material is dehydrated to form a solid. The nitrogen containing material may be selected from the group consisting of urea, manure, and combinations thereof. In other embodiments, the nitrogen containing material is urea and the aqueous material is saturated with urea. The aqueous material may be a slurry and it is also possible to include at least one additional nitrogen containing compound and/or at least one additional non-nitrogen plant nutrient to the aqueous material. A hardening agent may be further included in the aqueous material.
Surprisingly, when aeration is inhibited, calcium cyanamide and urea may be directly added to one another according to these methods, without significant loss of nitrogen, to yield a highly active cocktail. The cocktail may be preserved by dehydration and may be reactivated at a desired time and place by adding water. Also surprisingly, if the nitrogen containing material is manure, adding calcium cyanamide and inhibiting aeration serves to promote rapid (for example, a few hours to few days) release of soluble nitrogen and other nutrients from organic matter.
As will be discussed subsequently, what is even more surprising is that rapid composting of manures and also odor and microorganism inhibition are observed even at very low calcium cyanamide percentages. For example, when aeration is inhibited, liquidized manure with only 0.2 percent of the manure weight in solid calcium cyanamide exhibits these characteristics.
Thus, the methods of the disclosure rely in part on the discovery that inhibiting aeration of aqueous solutions of calcium cyanamide helps preserve the initial dissolution and hydrolysis products of calcium cyanamide. Aeration of aqueous solutions of calcium cyanamide appears to lead to increased precipitation of soluble calcium ions as insoluble calcium carbonate and to a reduction in pH that favors molecular cyanamide over acid cyanamide ions. Inhibiting aeration counteracts this effect. Any method of inhibiting aeration or combinations thereof may be used and specific, non-limiting examples include the following.
Aeration may be inhibited by simple techniques that provide relatively shorter periods of preservation of the desirable dissolution and hydrolysis products. For example, degassed water (e.g., boiled water, water subject to a vacuum, or nitrogen purged water) may be used instead of water in equilibrium with the atmosphere. Minimizing the vigor of mixing to slow dissolution of atmospheric gases into the water is another simple measure that may provide temporary stabilization of the liberated components of calcium cyanamide.
Other methods of inhibiting aeration that may provide for more controllable and longer preservation include the use of closed containers to inhibit exchange of gases with the atmosphere. A narrow opening or a loose fitting closure for such containers will provide some limited inhibition of aeration. Tight fitting or sealed closures (e.g., with a gasket or o-ring) are more desirable because gas exchange with the atmosphere is substantially prevented. When aqueous calcium cyanamide compositions are prepared and stored in sealed containers, they may be stored almost indefinitely.
Evacuation of the gases overlying an aqueous calcium cyanamide composition is another method of inhibiting aeration. Conversely, a gas that serves to substantially exclude the atmosphere may be added to a container. A gas may be added even if there is no closure on the container, provided the gas forms a dense blanket (e.g. argon) or is added to provide for constant gas outflow through the opening of the container. If the container is sealed a pressurized gas may further serve to expel the contents of the container and deliver the highly active aqueous compositions of this disclosure.
In particular embodiments the gas may be selected from the group consisting of nitrogen, acetylene, ammonia, argon, and mixtures thereof. In more particular embodiments, the gas is acetylene and the acetylene is generated from residual calcium carbide in the calcium cyanamide. Thus, surprisingly, when calcium cyanamide compositions are mixed with water (in at least 14xc3x97excess by weight relative to the calcium cyanamide content), in a container that is quickly sealed, a self-stabilizing highly active cocktail is obtained without any additional effort or additives. Furthermore, buffered by the calcium carbide gas, the resulting cocktail which contains only finely divided carbon rather than calcium carbonate balls and clumps may be sprayed, either directly or by injection into a chemigation/fertigation apparatus, without clogging.
Homogeneous granular materials according to the disclosure are also provided by a method of melting together a mixture of urea and calcium cyanamide, and then prilling, granulating, or spraying the melted mixture onto a seed particle to form a granule. In some embodiments, the seed particle is a particle of urea and in others, the seed particle is a particle of calcium cyanamide. The mixture of urea and calcium cyanamide and/or the seed particle may further comprise at least one additional ingredient, selected from the group consisting of nitrogen containing materials, non-nitrogen plant nutrients, and mixtures thereof.
The disclosure also includes aqueous compositions comprising greater than about 40 parts of water and about 10 parts of calcium cyanamide and urea combined, where the about 10 parts of calcium cyanamide and urea combined further comprises from about 0.1 to about 3 parts calcium cyanamide and from about 7 to about 9.9 parts urea. Desirably, aeration of such compositions is inhibited. Inhibition of aeration may be accomplished, for example, by preparing and keeping the composition in a closed container. In some embodiments a gas added to the container to inhibit aeration. It is also possible to inhibit aeration by any of the means discussed previously or subsequently. Such aqueous compositions may be either slurries or solutions.
Another discovery of the disclosure is that preservation of the initial dissolution and hydrolysis products of calcium cyanamide can be realized by combining small amounts of calcium cyanamide with animal excreta to provide stable, odor and microorganism inhibited compositions. Compositions comprising from about 0.01 to about 5.0 percent calcium cyanamide and from about 95 to about 99.99 percent animal excreta where the animal excreta further comprises water in an amount at least 14xc3x97 the weight of the calcium cyanamide are disclosed. In particular embodiments, such compositions may comprise from about 0.01 to about 1.0 percent calcium cyanamide and from about 99 to about 99.99 percent animal excreta, and still exhibit surprising properties. In other particular embodiments, the animal excreta is an aqueous slurry of manure.
One of the unexpected properties observed for aqueous calcium cyanamide/nitrogen containing material compositions, for example, aqueous calcium cyanamide/manure compositions, is that they quickly penetrate and flocculate soils. It is believed that soluble calcium ions and soluble nitrogen forms, such as urea, synergistically stabilize and facilitate transport of high pH aqueous calcium cyanamide compositions deep into soils. Inhibition of aeration until time of application of such compositions is desirable to effect full delivery of the initial dissolution and hydrolysis products of calcium cyanamide to the soil or growth medium.
The disclosure also provides methods of delivering nutrients to plants. In one embodiment, a calcium compound selected from the group consisting of calcium cyanamide, calcium oxide, calcium carbide, and mixtures thereof is added to water to form an aqueous composition and aeration is inhibited until the composition is applied foliarly or to soil (medium) to provide nutrients to plants. In a particular embodiment, the calcium cyanamide is commercial calcium cyanamide and it is added to at least 14xc3x97 its weight in water. The aqueous composition may be utilized as a sprayable slurry or optionally, solids may be removed from the aqueous composition before it is applied. Solids may be removed, for example, from the aqueous composition by a method selected from the group consisting of filtration, centrifugation, and decantation.
If urea or animal excreta are added to aeration inhibited aqueous compositions comprising a calcium containing compound, the synergistic soil amending action of soluble calcium and urea may provide improved delivery of all the nutrients in the composition. In various embodiments, urea may be added in an amount from about 0.01 percent by weight of the composition to about its saturation limit in the aqueous composition. Additional urea may be added if a slurry containing urea particles is desired.
In another alternative embodiment, aeration of aqueous calcium compound containing compositions is inhibited until the compositions are added to additional water and applied to plants, soils, or mediums through an irrigation system, for example a fertigation/nitrigation system.
Also disclosed are methods for enhancing plant growth by applying granular composition according to the disclosure directly to soil to induce plant growth. In one embodiment, a composition comprising a calcium cyanamide core and a urea shell where the calcium cyanamide core is from about 0.1 to about 40 percent by weight and the urea shell is from about 60 to about 99.9 percent by weight is applied to soil to induce plant growth.
Methods of enhancing plant growth by dissolution of the granular compositions of the disclosure in water are also included. For example, in one embodiment, a granular composition comprising a calcium cyanamide core and a urea shell, where the calcium cyanamide core is from about 0.1 to about 40 percent by weight and the urea shell is from about 60 to about 99.9 percent by weight is added to water to form an aqueous composition that is applied (to soil or foliarly) to enhance plant growth. In more particular embodiments, aeration of the aqueous composition is inhibited until the aqueous composition is applied to enhance plant growth.
As previously mentioned, methods of composting animal excreta are also disclosed. In one embodiment, about 0.1 to about 1.0 percent by weight calcium cyanamide is added to animal excreta where the animal excreta contains water in an amount at least 14xc3x97 the mass of calcium cyanamide added to form a mixture. In a particular embodiment, the animal excreta is liquidized manure.
Another disclosed method of composting animal excreta comprises adding about 0.1 to about 1.0 percent by weight calcium cyanamide to animal excreta where the animal excreta contains water in an amount at least 14xc3x97 the mass of calcium cyanamide to form a mixture; and inhibiting aeration of the mixture, for example by placing the mixture in a closed or sealed container. It is also possible to inhibit aeration by forming the mixture in a container, where the container also holds a gas, selected from the group consisting of nitrogen, argon, ammonia, acetylene, and mixtures thereof, that serves to inhibit gas exchange between the container and the atmosphere.
The calcium cyanamide that is added to the animal excreta according to these methods may be calcium cyanamide in a form selected from the group consisting of calcium cyanamide fines, granulated calcium cyanamide, a homogeneous granule comprising calcium cyanamide and urea, a heterogeneous granule comprising calcium cyanamide and urea, an aqueous composition comprising calcium cyanamide dissolved in greater than 14xc3x97 its weight in water, and mixtures thereof. Animal excreta composted according to the methods of the disclosure may be conveniently applied to soil using a slurry spraying apparatus.
Another disclosed method of enhancing plant growth comprises combining greater than about 40 parts of water with about 10 parts of a combination of calcium cyanamide and urea, where the about 10 parts of a combination of calcium cyanamide and urea further comprises from about 0.1 to about 3 parts calcium cyanamide and from about 7 to about 9.9 parts urea to form a first aqueous composition. Aeration of the first aqueous composition is inhibited and the first aqueous composition is diluted in additional water to form a second aqueous composition. The second aqueous composition is then applied to enhance plant growth.
The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description of several embodiments which proceeds with reference to the accompanying figures. The inclusion of particular embodiments in this Summary, does not imply that they are essential to the invention.